High frequency circulator comprising a plurality of non-reciprocal ferromagnetic circuits



March 21, 1967 NAOYUKI QGASAWARA 3,310,759

HIGH FREQUENCY CIRCULATOR COMPRISING A PLURALITY OF NQN-RECIPROCAL FERROMAGNETIC CIRCUITS Filed May 5, 1964 F/G/d l0 FERRO- M ,FERRO' MAGNET'C t5 MAGNETIC O O '5 O X /0 0e/s/ed United States Patent Claims. cl. ass-1.1

This invention relates to a non-reciprocal electric circuit such as an isolator, a directional phase-shifting circuit, a circulator composed of said non-reciprocal circuits, etc., wherein use is made of lumped-constant elements and the spin-resonance effect of a ferro-magnetic substance.

One conventional nonreciprocal circuit wherein use is made of the spin-resonance elfect of a ferromagnetic substance, includes: a rectangular or a circular Waveguide having a ferromagnetic body disposed at a point within a region where the so-called circularly polarized magnetic field (or, in truth, a rotating high-frequency magnetic field) appears when electromagnetic waves travel through the waveguide. A direct-current magnetic field is then produced in the space where the ferromagnetic body is disposed for establishing the spin-resonance effect of the ferromagnetic substance.

Another-type prior art non-reciprocal circuit includes: a coaxial line (which may be a pair of strip lines); a dielectric body formed of a suitable material in a suitable. shape which produces, when disposed between the inner and the outer conductors, a rotating high-frequency magnetic field whenever electromagnetic waves travel along the coaxial line. A ferromagnetic body is disposed at a point within the region of said rotating high-frequency magnetic field; and a direct-current magnetic field is produced in the space where the ferromagnetic body is disposed for enabling utilization of the spin-resonance effect of the ferromagnetic substance. Both of said prior art conventional non-reciprocal circuits (because they use distributed-constant circuits), suffer from the substantial defect that the dimensions of the circuit increase with increase of the wavelength of the electromagnetic waves.

7 HP or the VHF range.

, While I have described above the principles of my invention in connection with specific embodiments, it is to be clearly understood that this description is made only by way of example and not as a limitation to the scope of my invention as set forth in the objects thereof and in the accompanying claims.

FIG. 1(a) is an isometric projection of one type of a rotating high-frequency magnetic field device which includes: lumped-constant circuits and which can be used in a' non-reciprocal electric circuit of the invention;

FIG. 1(b), (0), (d), and (e) are enlarged plan views of magnetic field device shown in FIG. l-(a);

. Patented Mar. 21, 1357 FIG. 2 is a circuit diagram of an embodiment of the invention;

FIG. 3 is a graph showing the test measurements obtained from an experimental non-reciprocal circuit built in accordance with this invention; and

FIG. 4 shows the circuit of another embodiment of the invention.

Referring at first to FIG. 1(a), a rotating high-frequency magnetic field device 10 (which is an example of a device to be used in a non-reciprocal electric circuit of the invention) includes a magnet 11 with a ferromagnetic body 15 (supported by supporting means not shown) disposed in a direct-current magnetic field shown by arrow 14 which is produced between opposing pole pieces 12 and 13 of the magnet 11. Said magnetic field is substantially uniform at least within the space between the pole pieces 12 and 13. A first and a second winding 16 and 17 are wound around the ferromagnetic body 15 in the manner to be described hereinafter. The magnet 11, although illustrated as a horeshoe magnet, may be any I shape or type magnet which will produce the substantially uniform direct-current magnetic field shown by arrow 14 within the space where the windings 16 and 17 are to be placed. Thus, magnet 11 may be an electromagnet which will permit easy adjustment of said direct-current magnetic field. The magnetic core coil 18 includes the ferromagnetic body 15 and the windings 16 and 17 wound around the ferromagnetic body 15. Core coil 18 may be formed by winding coils 16 and 17 as illustrated in FIG- URE 1(b), on a ferromagnetic body 15' (which has a circular or a polygonal cylindrical shape of relatively small height and which is adapted to 'be supported within the direct-current magnetic field shown by arrow 14 with its axis disposed in the direction of the magnetic field 14). Said windings 16 and 17 each has several turns, and are electrically insulated from the ferromagnetic body 15' and from each other. Said windings are wound in such a manner that a first plane defined by substantially one turn of the winding 16 and a similar second plane defined by substantially one turn of the winding 17 are parallel to the direction of the direct-current magnetic field shown by arrow 14 and are perpendicular to each other. Such a magnetic core coil 18 can be supported 'Within the direct-current magnetic field shown by arrow 14 so as to be rotatable around the axis of the ferromagnetic body15. However, coil 18 is preferably supported to be immovable relative to said direct-current magnetic field because this simplifies construction. As shown in FIG. l(c), the magnetic core coil 18 may also be formed by winding the windings 16 and 17 around an insulator body 19 which has dimensions similar to those of the ferromagnetic body 15' illustrated in FIG. 1(b). In FIG. 1(a) a small ferromagnetic body 15 is buried in the area of crossing of the windings 16 and 17. The small ferromagnetic body 15" may be buried in the insulator body 19 by splitting the insulator body 19 into two parts. Recesses are then formed in said parts to receive the small ferromagnetic body 15". The parts are then joined together with the small ferromagnetic body 15" interposed, therebetween. If the magnetic core coil 18 is formed in the manner shown in FIG. 1(b), the magnetic core coil 18'may be formed as illustrated in FIG. 1(d) so that the magnetic paths for .the high-frequency magnetic fields produced by the respective high-frequency currents flowing through the windings 16 and 17 will be closed. Consequently the flux density of the high-frequency magnetic fields in the ferromagnetic body 15 will be large. Furthermore, a plurality of magnetic core coils 181, 182, 183, and so on may be combined, as shown in FIG. 1(e), into a compound magnetic core coil 18' by providing the ferromagnetic body 15 with means, such as slits 150, for preventing mutual interference. The above-mentioned planes relating to the windings 16 and 17 need not be perpendicular to each other but need only intersect each other.

Referring to FIG. 2, there is illustrated therein a circuit diagram for an embodiment of the invention. In FIG. 2 a rotating high-frequency magnetic field device is provided which has (as explained with reference to FIG. 1(a)) means for producing a substantially uniform direct-current magnetic field shown at 14 as coming out perpendicular to the plane of the paper. This magnetic field for example exists in a space which is about three centimeters in diameter (in cross-section) and a fraction of centimeter high. A ferromagnetic body 15 is disposed in the direct-current magnetic field 14. A first winding 16, of at least one turn, is wound around the ferromagnetic body 15 in such a manner that a plane defined substantially by the Winding may be substantially parallel to the direction of the direct-current magnetic field 14. A second winding 17, of at least one turn, is also Wound around the ferromagnetic body 15 in such a manner that a plane defined substantially by the winding may also be substantially parallel to the direction of the direct-current magnetic field 14 and intersects the above-mentioned plane relating to the winding 16. Connecting means is provided to connect a first end 161 (selected arbitrarily) of the first winding 16 and one end 171 (also arbitrarily selected) of the second winding 17 so that a high-frequency current can flow between the ends 161 and 171. A first pair of terminals 21 is connected to the connecting means 20 to supply and receive high-frequency current from both the first and the second windings 16 and 17. A second pair of terminals 22 is related to the other end 162 of the first winding 16 to supply and receive a high-frequency current to and from the first winding 16 (and consequently to and from the second winding 17). Means are provided (such as a variable capacitor 24 interposed between, for example, theother end 172 of the second winding 17 and the earth or similar return 23 for a highfrequency current flowing through the second winding 17) for adjusting (relative to each other) the phases of a first high-frequency current which flows through the first winding 16 and a second high-frequency current which flows through the second winding 17. The adjusting means adjusts the first high-frequency magnetic field component produced in the ferromagnetic body 15 by the first high-frequency current and the second highfrequency magnetic field component also produced in the ferromagnetic body 15 by the second high-frequency current to be in phase quadrature relationship (or have a phase difference of 190). Said adjusting means preferably adjust (relative to each other) the waveforms of the first and the second high-frequency currents so that the first and the second high-frequency magnetic field components have either a waveform identity relationship, or so that each of said components includes at least one sinusoidal wave magnetic field whose amplitude is substantially equal to that of the corresponding sinusoidal wave magnetic field of the other. Preferably, the above-mentioned planes relating to the first and the second windings 16 and 17 are made substantially perpendicular to each other. The embodiment of FIG. 2 is further provided with first means (related to a first circuit generally shown at 25 which includes the first winding 16 and is interposed between the first and the second terminal pairs 21 and 22) for placing the first circuit 25 in a series resonance state at the frequency of the first high-frequency current (such as a variable capacitor 26). Said capacitor 26 may be interposed between, for example, the end 162 of the first winding 16 and the second pair of terminals 22. FIG. 2 also includes second means related to a second circuit generally indicated at 27 (including the second winding 17) interposed between the connecting means 211 and the return 23, for maximizing the impedance of the second be an inductive reactance element in the event the second circuit 27 exhibits a capacitive effect, so that the second high-frequency current may lead the first highfrequency current. Element 28 may be a capacitive reactance element in the event the second circuit 27 exhibits an inductive effect so that the second high-frequency current may lag behind the first high-frequency current.

Continuing to refer to FIG. 2, the purpose of the embodiment of the invention shown therein may be to measure the characteristics of the non-reciprocal circuit. In this event, a signal generator 30 is connected to the first terminal pair 21 and a power meter or a phase shift meter 31 is connected to the second terminal pair 22. When the non-reciprocal circuit has the preferable construction mentioned above, the first high-frequency current is supplied from the signal generator 3%) to the non-reciprocal circuit and flows through the first winding where it is attenuated and shifted in phase in accordance with the sense and magnitude of the directcurrent magnetic field shown as 14 and thereafter flows to the power meter or the phase shift meter 31. It is to be noted here that the provision of the connecting means 20 between the ends 161 and 171 of the first and the second windings 16 and 17 makes it easy to establish the phase quadrature relationship and the waveform identity relationship between the first and the second high-frequency magnetic field components, or to form in the ferromagnetic body 15 a rotating high-frequency magnetic field whose instantaneous amplitude does not vary with time. If the spin resonance is substantially perfect (or if the frequency of the rotating high-frequency field determined by the first high-frequency current) is substantially equal to the gyrofrequency, (determined by-the ferromagnetic or magnetic substance of which the ferromagnetic or magnetic body 15 is composed and by the magnitude of the directcurrent magnetic field 14) then the power meter 31 will show that the first high-frequency current reaches the second pair of terminals 22 either without any appreciable attenuation or with remarkable attenuation. In this case, if a high-frequency current is caused to travel through the non-reciprocal circuit (i.e. between the pair of terminals 21 and 22) in a first sense from one to the other of said terminal pairs 21 and 22 and it does not undergo any appreciable attenuation, then another highfrequency current having substantially the same frequency as the first-mentioned high-frequency current and traveling from one to the other of said terminal pairs through the same non-reciprocal circuit in an opposite sense with respect to the first sense will undergo remarkable attenuation. Therefore, it is seen that the nonreciprocal circuit serves as an isolator. In case the spin resonance is not perfect, or if either the rotating highfrequency magnetic field or the various frequency relationships, or both, are not as perfect as has been above described (but are in more general states), then the phase shift meter 31 will indicate that the phase shift ofa high-frequency current flowing through the non-reciprocal circuit in the first sense and of another highfrequency current traveling through the same non-reciprocal circuit in the second sense are different from each other by an amount determined by the sense and the magnitude of the direct-current magnetic field generally indicated by 14 and by the relationships among the frequencies, the intensities, and the phases of the aforementioned first and second high-frequency currents. In this latter case, the non-reciprocal circuit serves as a directional phase-shifting circuit.

Referring now to FIG. 3, a graph is illustrated therein whose abscissa axis indicates the magnitude of the direct current magnetic field H generally shown by 14 and the ordinate axis shows the attenuation A which the nonreciprocal circuit illustrated in FIG. 2 imparts to a highfrequency current flowing therethrough. Curves 35 and 36 are respectively plots of (1) the large attenuation (or the isolation) which a high-frequency current undergoes while passing through the non-reciprocal circuit in one of the senses and (2) of the small attenuation or the insertion loss which another high-frequency current of substantially the same frequency as the first-mentioned high-frequency current undergoes while traveling through the same non-reciprocal circuit in the reversed sense. The curves 35 and 36 are the actual measured results when high-frequency currents (whose common center frequency is l40mc.) were made to flow through a nonreciprocal circuit having the preferable construction explained above with reference to FIG. 2 and wherein the magnetic core coil 18 was a disc-shaped ferromagnetic body 15 formed of a manganese-magnesium-aluminum ferrite designated 6-26 and sold by TDK Electronics Company, Limited of Tiyo-da-ku, Tokyo-to, Japan. Said core coil 18 was about 18 millimeters in diameter and about 6 millimeters in height and was provided with windings 16 and 17, each having several turns, and whose planes (as mentioned above) were disposed perpendicular to each other.

Finally referring to FIG. 4, another circuit embodiment of the invention is illustrated therein. In this embodiment a first, a second and a third non-reciprocal circuit unit 401, 402, and 403 are provided. Each of said units has a similar construction to the non-reciprocal circuit explained with reference to FIG. 2, and furthermore substantially identical to each other. These units are interconnected in a delta configuration so that at least for the high-frequency current, the pair of terminals 41 acts as both the second terminal pair for circuit unit 401 and the first terminal pair for unit 402. Additionally, the pair of terminals 43 act in' a similar manner for units 403 and 401 and terminal pair 402 acts in a similar manner for units 402 and 403. In FIG. 4, separate ferromagnetic bodies 101, 102, 103 are respectively provided for the first, the second, and the third nonreciprocal circuit units 401, 402, and 403. Separate magnetic fields 104, 105, 106 are shown for said bodies. It is possible in practice to unite, (in the manner shown in FIG. l(e)) the magnetic core coils for such nonreciprocal circuit units together into a compound magnetic core coil regardless of the number of non-reciprocal circuit units, and to disposesuch a compound magnetic core coil in a direct-current magnetic field produced by a single magnet.

Again, referring to FIG. 4, if the compound nonreciprocalcircuit, is adjusted so that a high-frequency current transmitted from the first terminal pair 41 through the circuit unit 402 to the second terminal pair 42 undergoes a phase shift of 120 while another high-frequency current which has substantially. the same frequency as the first-mentioned high-frequency current and which is transmitted through the same circuit unit 402 from the second terminal pair 42 to the first terminal pair 41 undergoes a phase shift of 60 and if said compound circuit is adjusted so that said high-frequency currents which have substantially the same frequency as the common frequency of the aforementioned two high-frequency currents and which are transmitted through units 403 and 401 in one and the other sense also undergo phase shifts of 120 and 60, respectively, then high-frequency current supplied from the first terminal pair 41 will travel through two paths to the terminals 42, first through unit 402 to the second terminal pair 42 for a total phase shift of 120 and second through units 401 and 403 also with a phase shift of 120. Thus, the partial high-frequency currents transmitted to the second terminal pair 42 through separate transmission paths will appear at the second terminal pair 42 in phase or in an additive manner. The partial high-frequency currents transmitted to the third terminal pair 43 through separate transmission paths will appear at the third terminal pair 43 in phase opposition or in a differential manner. Therefore, the compounded non-reciprocal circuit of FIG. 4 if adjusted in the above-mentioned manner and if the first, the second, and the third terminal pairs 41, 42, and 43 are terminated in the respective input and/or output circuits having impedances determined with reference to the characteristic impedances of the non-reciprocal circuit units 401, 402, and 403, will serve as a three-port circulator with the sense of circulation shown in the drawing by an arrow 44.

While I have described above the principles of my invention in connection with specific embodiments, it is to be clearly understood that this description is made only by way of example, and not as a limitation to the scope of my invention as set forth in the objects thereof and in the accompanying claims.

What is claimed is:

1. A compound non-reciprocal circuit comprising:

a plurality of non-reciprocal circuits each being comprised of:

(A) a ferromagnetic body; (B) first and second windings wound around said body such that: I

(1) each of said windings has at least one turn, (2) each turn of each winding defines a plane,

(a) the plane defined by said second winding intersecting the plane defined bysaid first winding,

(3) said windings being insulated from said body and from each other;

(C) connection means for interlinking a first end of the first winding Wtih a first end of said second winding at a common terminal to permit high frequency current exchange between said windings;

(D) first means directly connected to said connection means and second means connected to the second end of said first winding for supplying high frequency current to said windings, the supplied high frequency currents producing different high frequency current components in each of said windings, which components, in turn, respectively produce different magnetic field components in said ferromagnetic body;

(E) said first and second means each including 1 means for receiving high frequency current from said windings;

(F) adjusting means each being coupled to an associated winding for adjusting the phase of said high frequency current components relative to each other, to thereby control said magnetic field components produced in said body; and

(G) means for applying a uniform direct current magnetic field to said windings in a direction parallel to the planes defined by said windings whereby for a preselected ferromagnetic body and a predetermined direct current magnetic field, the spin resonance effect on said body can be controlled to regulate simultaneously the currents flowing in either direction from said first means to said second means;

(H) means for serially interconnecting said circuits to form a closed loop such that each first means is simultaneously coupled to the common terminal of at least one of said non-reciprocal circuits and to the sec-0nd end of the first winding of at least one other non-reciprocal circuit.

7 8 2. A compound non-reciprocal circuit comprising: 5. A lumped-constant three-port circulator comprising: a plurality of non-reciprocal circuits each being coma first, second and third non-reciprocal circuit unit;

prised of: each of said non-reciprocal circuit units comprising:

(A) a ferromagnetic body; (B) first and second windings wound around said (A) a ferromagnetic body; (B) a first winding and a second winding Wound body such that: around said ferromagetic .body, said windings (1) each of said windings has at least one lying in substantially mutually perpendicular turn, planes, respectively, intersecting along a line, one

(2) each turn of each winding defines a plane, (a) the plane defined by said second end of said first winding being connected with one end of said second winding serving as a first winding intersecting the plane defined terminal for receiving high frequency current; by said first Winding, (C) a first variable tuning capacitor having one (3) said windings being insulated from said of its electrodes connected to the other end of body and from each other; said first winding and a second variable tuning (C) connection means for interlinking a first end 5 capacitor connected between the other end of of the first winding wtih a first end of said secsaid second Winding and ground, the other elecond winding at a common terminal to permit trode of said first variable tuning capacitor servhigh frequency current exchange between said ing as-a second terminal, said first and second windings; variable tuning capacitors serving to adjust the (D) first means directly connected to said conthe relative shift in phase between a first and nection means and second means connected to a second H-F current component caused to flow the second end of said first winding for supplythrough in said first and said second windings, I ing high frequency current to said windings, the respectively, by the high frequency current supsupplied high frequency currents producing difplied to said first terminal so that the H-F magferent high frequency current components in netic fields induced in said ferromagnetic body each of said windings, which components, in by said first and said second H-F current comturn, respectively produce different magnetic ponents, respectively, may be substantially in field components in said ferromagnetic body; quadrature phase relation to each other; and (E) said first and second means each including (D) magnet means for gentrating aD.C. magnetic means for receiving high frequency current from field having a homogeneous field intensity; said said windings; two windings being disposed in said D.C. magnet- (F) adjusting means each being coupled to an ic field such that the direction of the field is associated winding for adjusting the phase of substantially parallel to the plane of said windsaid high frequency current components relaings; each of said non-reciprocal circuit units tive to each other, to thereby control said mag being adjusted in such a manner that a first s-ignetic field components produced in said body; nal travelling from the first terminal to the and second terminal undergoes a phase shift of 60 (G) means for applying a uniform direct current degrees and a second signal travelling from the magnetic field to said windings in a direction second terminal to the first terminal undergoes parallel to the planes defined by said windings a phase shift of 120 degrees; said three nonwhereby for a preselected ferromagnetic body reciprocal circuit units being interconnected to and a predetermined direct current magnetic form a closed loop such that the first terminal field, the spin resonance effect in said body can of said first non-reciprocal circuit unit is conbe controlled to regulate simultaneously the curnected with the second terminal of said second rents flowing in either direction from said first non-reciprocal circuit unit, the first terminal means t aid Second means; of said second unit is connected with the second means connecting said nonq-eciprocal circuits terminal Of said third unit, and the first terminal in a closed loop such that the second end of the of i third P is f W the second first winding of each non-reciprocal circuit is terminal of Sald first connected to the common terminal of an adja- References Cited by the Examimr cent non-reciprocal circuit. 3. The compound non-reciprocal circuit of claim 2 UNITED STATES PATENTS further comprising means connecting the second ends of 2,944,229 7/1960 DeVries 333--24.2 the second windings to a common terminal. 3,010,085 11/ 1961 Seidel 333-24.2 4. The compound non-reciprocal circuit of claim 3 3,038,133 6/ 1962 DeVries comprising three non-reciprocal circuits;

said first windings being connected in delta fashion; HERMAN KARL SAALBACH Pnmary Exa'mmer" said second windings being connected in Y fashion. P. L, GENSLER, Assistant Examiner, 

1. A COMPOUND NON-RECIPROCAL CIRCUIT COMPRISING: A PLURALITY OF NON-RECIPROCAL CIRCUITS EACH BEING COMPRISED OF: (A) A FERROMAGNETIC BODY; (B) FIRST AND SECOND WINDINGS WOUND AROUND SAID BODY SUCH THAT: (1) EACH OF SAID WINDINGS HAS AT LEAST ONE TURN, (2) EACH TURN OF EACH WINDING DEFINES A PLANE, (A) THE PLANE DEFINED BY SAID SECOND WINDING INTERSECTING THE PLANE DEFINED BY SAID FIRST WINDING, (3) SAID WINDINGS BEING INSULATED FROM SAID BODY AND FROM EACH OTHER; (C) CONNECTION MEANS FOR INTERLINKING A FIRST END OF THE FIRST WINDING WITH A FIRST END OF SAID SECOND WINDING AT A COMMON TERMINAL TO PERMIT HIGH FREQUENCY CURRENT EXCHANGE BETWEEN SAID WINDINGS; (D) FIRST MEANS DIRECTLY CONNECTED TO SAID CONNECTION MEANS AND SECOND MEANS CONNECTED TO THE SECOND END OF SAID FIRST WINDING FOR SUPPLYING HIGH FREQUENCY CURRENT TO SAID WINDINGS, THE SUPPLIED HIGH FREQUENCY CURRENTS PRODUCING DIFFERENT HIGH FREQUENCY CURRENT COMPONENTS IN EACH OF SAID WINDINGS, WHICH COMPONENTS, IN TURN, RESPECTIVELY PRODUCE DIFFERENT MAGNETIC FIELD COMPONENTS IN SAID FERROMAGNETIC BODY; (E) SAID FIRST AND SECOND MEANS EACH INCLUDING MEANS FOR RECEIVING HIGH FREQUENCY CURRENT FROM SAID WINDINGS; (F) ADJUSTING MEANS EACH BEING COUPLED TO AN ASSOCIATED WINDING FOR ADJUSTING THE PHASE OF AND HIGH FREQUENCY CURRENT COMPONENTS RELATIVE TO EACH OTHER, TO THEREBY CONTROL SAID MAGNETIC FIELD COMPONENTS PRODUCED IN SAID BODY; AND (G) MEANS FOR APPLYING A UNIFORM DIRECT CURRENT MAGNETIC FIELD TO SAID WINDINGS IN A DIRECTION PARALLEL TO THE PLANES DEFINED BY SAID WINDINGS WHEREBY FOR A PRESELECTED FERROMAGNETIC BODY AND A PREDETERMINED DIRECT CURRENT MAGNETIC FIELD, THE SPIN RESONANCE EFFECT ON SAID BODY CAN BE CONTROLLED TO REGULATE SIMULTANEOUSLY THE CURRENTS FLOWING IN EITHER DIRECTION FROM SAID FIRST MEANS TO SAID SECOND MEANS; (H) MEANS FOR SERIALLY INTERCONNECTING SAID CIRCUITS TO FORM A CLOSED LOOP SUCH THAT EACH FIRST MEANS IS SIMULTANEOUSLY COUPLED TO THE COMMON TERMINAL OF AT LEAST ONE OF SAID NON-RECIPROCAL CIRCUITS AND TO THE SECOND END OF THE FIRST WINDING OF AT LEAST ONE OTHER NON-RECIPROCAL CIRCUIT. 